1. Field of the Invention
The present invention relates to a connecting structure of a cell monitor connector to a fuel cell stack.
2. Description of Related Art
A fuel cell (for example, a polymer electrolyte fuel cell) includes a membrane-electrode assembly (MEA), a diffusion layer, and a separator. The MEA includes an electrolyte membrane and a pair of electrodes disposed on opposite sides of the electrolyte membrane. The pair of electrodes include an anode provided on one side of the membrane and constructed of a first catalyst layer and a cathode provided on the other side of the membrane and constructed of a second catalyst layer. A first diffusion layer is provided between the first catalyst layer and the separator, and a second diffusion layer is provided between the second catalyst layer and the separator. The separator has a passage formed therein for supplying fuel gas (hydrogen) to the anode and a passage formed therein for supplying oxidant gas (oxygen, usually, air) to the cathode. A module is constructed of at least one layer of a fuel cell. A number of modules are layered, and electrical terminals, electrical insulators, and end plates are disposed at opposite ends of the pile of modules to construct a stack of fuel cells (a fuel cell stack). After tightening the stack of fuel cells between the opposite end plates in a fuel cell stacking direction, the end plates are coupled to a fastening member (for example, a tension plate) extending in the fuel cell stacking direction outside the pile of fuel cells by bolts.
In the fuel cells, at the anode, hydrogen is changed to positively charged hydrogen ions (i.e., protons) and electrons. The hydrogen ions move through the electrolyte membrane to the cathode where the hydrogen ions react with supplied oxygen and electrons (which are generated at an anode of the adjacent MEA and move to the cathode of the instant MEA through a separator, or which are generated at an anode of the MEA located at one end of the pile of fuel cells and move to the cathode of the MEA located at the other end of the pile of the fuel cells through an outer electrical circuit) to form water as follows:
At the anode: H2→2H++2e−
At the cathode: 2H++2e−+(1/2)O2→H2O
Since heat is generated at the above water product reaction and Joulean heat, a coolant passage (usually, a water passage) is formed in the separator to cool every fuel cell or every plural fuel cells.
To confirm that power is normally generated at the fuel cells, to control the flow of the reactant gas based on the cell voltage, and to protect a motor from an abnormal voltage, a cell voltage is monitored every fuel cell or every plural fuel cells.
Japanese Patent Publication No. HEI 9-283166 discloses a connecting structure of a cell monitor connector to a fuel cell stack where two circular holes are formed in the separators of every fuel cell, and more particularly, one hole is formed in a cathode side separator of the fuel cell and the other hole is formed in an anode side separator of the same fuel cell, and a pin terminal of the cell monitor connector is inserted into the one hole and another pin terminal of the cell monitor connector is inserted into the other hole.
However, with the conventional connecting structure of a cell monitor connector (a connector of a cell monitor) to a fuel cell stack, there is a problem that since each fuel cell is very thin, the terminal contacting the cathode side separator of a fuel cell and the terminal contacting the anode side separator of the same fuel cell interfere with each other and cannot be arranged.
Further, when a plurality of fuel cell stacks are provided, since numerous cell monitor connectors contact a fuel cell stack, the connecting structure of a cell monitor including the cell monitor connectors is complex and occupies a relatively large space.